The invention relates to apparatus for transporting rod-shaped articles of the tobacco processing industry and/or their components. More particularly, the invention relates to improvements in apparatus for pneumatically transporting filter rod sections, plain or filter cigarettes, cigars or cigarillos as well as cigarette paper, tipping paper, filter paper and blanks of paper or other material for use in the making of packets for cigarettes and the like.
It is customary to transport rod-shaped articles of the tobacco processing industry and their components on drum-shaped rotary conveyors which are formed with suction ports to attract the conveyed objects. Connection with a stationary suction generating device (e.g., a fan or a suction pump) is established by way of a stationary valve plate which abuts one axial end of the body of the rotating drum-shaped conveyor. If the objects to be transported are rods (e.g., plain or filter cigarettes, cigars or cigarillos, filter rod sections, tubular shells of paper or the like), the peripheral surface of a rotary suction drum is normally formed with axially parallel flutes which receive portions of or even the entire rod-shaped articles, and the suction ports are machined into those surfaces of the drum-shaped conveyor which surround the flutes. The peripheral surface of a rotary drum-shaped conveyor is a smooth cylinder if the conveyor is used to transport continuous webs or strips of cigarette paper, filter paper, tipping paper or other wrapping material as well as if the conveyor is used to transport discrete sections of strips or webs, e.g., individual blanks of paper, foil or cardboard in a cigarette packing machine or individual sections of tipping paper in filter tipping machines wherein plain cigarettes are united with filter plugs to form filter cigarettes of unit length or multiple unit length.
The suction ports of a conventional rotary suction drum are substantially radially disposed holes or bores which extend from the peripheral surface to axially parallel bores extending to one end face of the drum body to be connected with a suction generating device, at least during one or more stages of each revolution of the drum. As mentioned above, the suction ports are normally disposed in rows extending in parallelism with the axis of the suction drum, and the length of each row of suction ports is related to the length of rod-shaped articles or to the width of sheet-like objects which are to be transported by the drum. Consequently, if a suction drum is designed to transport relatively short rod-shaped articles (which are parallel to the axis of the drum) or to transport relatively narrow strips of cigarette paper or the like, such drum cannot be used for the transport of longer articles (e.g., plain cigarettes of double unit length) or for the transport of relatively wide strips or webs. Therefore, it is often necessary to employ relatively long drums for the transport of short rod-shaped articles or for the transport of relatively narrow strips or webs because this ensures that the same drum can be used for the transport of longer rod-shaped articles or wider webs or strips.
A drawback of a drum-shaped conveyor wherein the length of rows of suction ports exceeds the length of rod-shaped articles or the width of strip-shaped commodities is that certain suction ports remain exposed when the conveyor is in use. Streams of air which flow into exposed suction ports are likely to entrain solid contaminants (such as minute fragments of cigarette paper and/or minute fragments of tobacco) which clog the passages between the ports and the suction generating device. Another drawback of air streams which are free to flow into exposed suction ports is that they generate considerable noise.
In order to avoid the above outlined drawbacks of relatively long drum-shaped penumatic conveyors, it is customary to seal those suction ports which would remain exposed if the conveyor were used for the transport of relatively short rod-shaped articles of for the transport of relatively narrow strips of webs of paper or the like. This involves much work and prolongs the intervals of idleness of the machine in which the conveyor is put to use. In accordance with another known proposal, a relatively long drum-shaped conveyor is replaced with a shorter conveyor if the transport of a series of relatively long articles or wide webs is to be followed with the transport of a series of shorter articles or narrower webs. This, too, takes up much time and renders it necessary to maintain a supply of spare conveyors which contributes significantly to the initial cost of a cigarette maker, filter tipping machine, cigarette packing machine or any other machine which is used for the processing of smokers' products.